Hi Nick,
I think you raise an interesting point and it is one that isn't discussed here often. I suspect that meditation/ altered states of reality and hallucinogenic drugs all must have played a part in our human evolution and belief systems. Julian Cope touches on the subject of rock art patterns and hallucinogens in TME (the similarity of some swirling, spiral patterns to closed eye hallucinations).
Maybe such experiences are as close as we can get to understanding the ancient mind as they can enable us to sublimate our modern-thinking ego and be immersed in the place and moment?
Don't be disappointed if folk seem a bit reticent on this subject round here. I think people are wary of being branded nutter of the month!
I don't have any earth shattering personal anecdotes regarding ancient sites I am afraid, although I do find being stoned sometimes enhances the feel and experience of some sites.
But being stoned enhances Emmerdale as well, so......
Do you have any such anecdotes yourself?